1. Field of the Invention
The present invention relates to a gear widely used in a power transmission mechanism of automobiles, precision machineries, industrial machineries, components used therein, and the like.
2. Description of the Related Art
Various modifications have been made to enhance tooth strength in gears used in power transmission mechanisms of automobiles, precision machineries, and the like.
FIG. 19 is a diagram of a tooth form shape of such a gear 100. In the gear 100 shown in FIG. 19, the shape of a tooth 101 on the bottom side is an arch-shaped curved surface 102 matching a trajectory of motion of a tooth of a meshing partner gear (pinion) to an extent in which the arch-shaped curved surface 102 does not interfere with the trajectory. Tooth strength is enhanced by the position of a critical section in a 30° tangent method being moved closer to the top side, from P1 to P2 (refer to Patent Literature 1).    Patent Literature 1: Japanese Patent Laid-open Publication No. 2004-519644
However, in the gear 100 shown in FIG. 19, the arch-shaped curved surfaces 102 and 102 of adjacent teeth 101 and 101 merge, forming a pointed triangular peak 103 at the bottom. Therefore, in the gear 100 shown in FIG. 19, stress tends to be concentrated at the peak 103 at the bottom. There is a demand for strength enhancement of the overall tooth 101 including the bottom.